Bug 1913565 - Remove incorrect enlargement of single view array. r=welpy-cw,mkmelin

Extra fix: Remove unused variable.

Differential Revision: https://phabricator.services.mozilla.com/D219397

--HG--
extra : amend_source : 97ad4287154eda46c022187df82b56e2f0ae7328

mailnews/base/src/nsMsgDBView.cpp

@@ -4826,11 +4826,6 @@ nsresult nsMsgDBView::ExpandByIndex(nsMsgViewIndex index,
   nsresult rv = GetThreadContainingIndex(index, getter_AddRefs(pThread));
   NS_ENSURE_SUCCESS(rv, rv);
   if (m_viewFlags & nsMsgViewFlagsType::kUnreadOnly) {
-    // Keep top level hdr in thread, even though read.
-    if (flags & nsMsgMessageFlags::Read) {
-      m_levels.AppendElement(0);
-    }
-
     rv = ListUnreadIdsInThread(pThread, index, &numExpanded);
   } else {
     rv = ListIdsInThread(pThread, index, &numExpanded);

mailnews/base/src/nsMsgThreadedDBView.cpp

@@ -784,7 +784,6 @@ nsresult nsMsgThreadedDBView::RemoveByIndex(nsMsgViewIndex index) {
     // flags set correctly.
     if (threadHdr) {
       nsMsgDBView::RemoveByIndex(index);
-      nsCOMPtr<nsIMsgThread> nextThreadHdr;
       // Above RemoveByIndex may now make index out of bounds.
       if (IsValidIndex(index) && numThreadChildren > 0) {
         // unreadOnly